Flickering excitation LED with longer coax cable

[Jesper.vernooij]

Hi Everyone,

We have recently build a new miniscope featuring a 4' (~1,21m) coax cable. All components work as they should but the excitation LED flickers in strength quite some. In addition, whenever we connect our older miniscopes, the LED shines a little bit on 0% excitation power. The new LED first turns on at 20% power. For a full image: the older working miniscopes feature roughly 1,5' (45cm) cables. Does anyone know if the length of the cable is a factor in excitation LED power output and stability? Or did I just do a bad job soldering?

Thanks!

Jesper

[MikerVee]

We have 10 scopes in use with 3m coax cables. No problems with 9 of them.
Recently I replaced the LED on the 10th one because it was flickering and getting dimmer during a short period of operation. My guess is, the LED was degraded during the soldering process, maybe it got too hot. Some LEDs are very sensitive to that. Problem seems solved now.

[Daniel Aharoni]

Hi Jesper,
If using the coax cable from Cooner Wire (or something similar) you should be able to run up to (and likely well over) 10' without issue. The source of the flickering LED is likely one of the following;

• Most likely, as MikerVee said, the LED is damaged and needs to be replaced. Once the silicone lens/protector is removed from the LED it can be damaged by direct contact with the light emitting surface when inserting it into the Miniscope body.
• The coax cable has been damaged or has a kink in it that causes a poor connection sometimes.
• The coax cable connectors (possibly the coax cable soldered onto the DAQ PCB) has an issue. You can try redoing the soldering of these connectors.
• If you have version 3.2 of the CMOS PCB, make sure the 2 hald circles on the bottom of the PCB are shorted together with solder.
• Try a different computer. At higher LED power, the LED draws a decent amount of current. It is possible that your computer/USB port is not outputting enough current. This is unlikely.

[Jesper.vernooij]

Thanks for all the tips! I replaced the LED and everything works fine now. Must have indeed been damage from the solder job.